Elon Musk’s plans to turn Twitter Inc. into a free speech haven could run into its biggest political obstacles in the European Union, where he has to contend with its new Digital Services Act, which forces companies to take down illegal content. Musk said he’ll follow national laws — and specifically reassured concerned EU officials that he’ll follow the DSA — but this will be difficult in practice with so few staff left to moderate content. It won’t be easier in the EU’s lawmaking capital of Brussels, where Twitter’s office is now lifeless. EU leaders know Musk himself was a...